1. Field Of The Invention
The invention relates to a circuit breaker used for protecting an electric apparatus and a circuit from an overcurrent by maintaining the electric power supply to the electric apparatus while a normal current flows in the circuit and cutting off the power supply when an overcurrent flows in the circuit.
2. Description Of The Prior Art
There has been used a circuit breaker having structure as shown in FIG. 8 for example.
A circuit breaker 101 shown in FIG. 8 is provided with a first conductive plate 105 having a connecting terminal 102 and a base part 104 fixed with a bimetal 103 by spot welding (at the position marked in the figure with "X"), and with a second conductive plate 112 having a connecting terminal 110 and a terminal 111 attached with a fixed contact 111a contacting with or discontact from a moving contact 103a attached to said bimetal 103. And the base part 104 of said first conductive plate 105 and the second conductive plate 112 are formed in one body together with an insulator 113 by insert molding process.
In the circuit breaker 101, when an overcurrent flows in the bimetal 103, the moving contact 103a provided to said bimetal 103 is disconnected from the fixed contact 111a by the thermal deformation of said bimetal 103. Thereby, the electric power supply to the electric apparatus is cut off, the electric apparatus and the circuit are protected from the burning out caused by the overcurrent. And when the bimetal return to its original shape by the thermal drop during the interception of the power supply, said moving contact 103a comes in contact with the fixed contact 111a and the power supply to the electric apparatus is resumed. Hereupon, said circuit breaker 101 of the cycle type is so designed that an effective current descreases to the value lower than the burning current of the electric apparatus while the interception of the power supply caused by the overcurrent and the resumption by the thermal drop of the bimetal are repeated alternately, therefore it serves to prevent the electric apparatus and the circuit from the burning out. Additionally, said circuit breaker 101 is not actuated by a normal load current.
In the case of housing the circuit breaker on the inside of the electric apparatus such as a wiper motor or the like, it is necessary to miniaturize the circuit breaker in order to facilitate the housing. However, in the conventional circuit breaker 101 which is formed in one body by uniting the both conductive plates 105 and 112 together with the insulator 113 using the process of insert molding as described above, there is a problem in that the assembling operationability becomes worse owing to the miniaturization of the respective members of said circuit breaker.